I've noticed that whenever I have 12 or more pdf files open at one time (each in a separate window) and attempt to open an additional pdf, this additional pdf opens in the same window as the pdf on top. In other words, it's as if the "Open each file in its own window" is disabled once I reach 12 open pdfs.
I can then transfer the newly-opened pdf to a new window by right-clicking on the pdf's thumbnail and selecting "Open in New Window" but I don't want to have to do that every time I want to open an additional file. Does anyone know how I can make this happen?
Again, I already have the "Open each file in its own window" option enabled (and it works when I have less 12 pdfs already opened).
Lastly, assuming this is deliberate on Apple's part (i.e. not some sort of bug), is there a reason why I should be wary of opening up more than 12 pdfs in separate windows? And what other options are there for opening up pdfs in OS X other than via Preview? (I'm sure there are plenty of third-party apps available but I'm particularly interested in built-in alternatives).
[Note: A similar issue was mentioned here: Difficulties opening PDFs in Preview but the solution offered doesn't apply.]
OS X - Macbook Pro;
[EDIT: This behavior has occurred periodically for a while now (months)--it seems to occur after I've opened files in Preview that have been saved as PDFs via the "Save as PDF" option from the "Print" window.]